Integrated optical devices for directly processing optical signals have become of greater importance as optical fiber communications increasingly replace metallic cable and microwave transmission links. Integrated optical devices can advantageously be implemented as silica optical circuits having compact dimensions at relatively low cost. Silica optical circuits employ integrated waveguide structures formed on silicon substrates.
In some applications, optical gratings are formed in the silicon substrate or chip for input-output of the photonic signal. Typically, the optical grating is formed on a major surface of the silicon substrate. Hence, the photonic signal path extends largely perpendicular to the silicon substrate. When using the silicon substrate in coupling applications, such as when coupling to an optical fiber, the optical fiber must be mounted in near perpendicular fashion. In these applications, the side profile of the coupling device can be quite large, which is generally undesirable. Indeed, since optical fibers have a minimum bending radius, the side profile of the device can be substantially impacted.